1. Field of the Invention
Without limiting its scope, this invention relates to improved materials appropriate for use in an apparatus for creating three-dimensional objects, and more specifically, to materials and a method of utilizing such materials in Selective Deposition Modeling (SDM) of Thermal Stereolithography TSL Type Rapid Prototyping and Manufacturing (RP&M) Systems.
2. Background Information
Various approaches to automated or partially automated three-dimensional object production or Rapid Prototyping and Manufacturing have become available in recent years. These approaches are generally characterized by the building up of the three-dimensional objects from computer data descriptive of the object in an additive manner from a plurality of formed and adhered layers, each layer representing a cross-section of the three-dimensional object. Typically, successive layers of the object are formed and adhered to a stack of previously formed and adhered layers. In some RP&M technologies, techniques have been proposed which deviate from a strict layer-by-layer build up process by only partially forming an initial layer followed by partial formation of at least one subsequent layer and then finally followed by completing the formation of the initial layer.
According to one such approach, a three-dimensional object is built up by applying successive layers of unsolidified, flowable material to a working surface, and then selectively exposing the layers to synergistic stimulation in desired patterns, causing the layers to selectively harden into object cross-sections which adhere to previously-formed object cross-sections. In this approach, material is applied to the working surface both to areas which will not become part of an object cross-section, and to areas which will become part of an object cross-section. Typical of this approach is Stereolithography, as described in U.S. Pat. No. 4,575,330 to Hull. According to one embodiment of Stereolithography, the synergistic stimulation is radiation from a UV laser, and the material is a photopolymer. Another example of this approach is Selective Laser Sintering, as described in U.S. Pat. No. 4,863,538, Deckard, in which the synergistic stimulation is radiation from a CO.sub.2 laser and the material is a sinterable powder. A third example is Direct Shell Production Casting, as described in U.S. Pat. Nos. 5,340,656 and 5,204,055 to Sachs, et al., in which the synergistic stimulation is a chemical binder, and the material is a powder consisting of particles which bind together upon application of the chemical binder.
According to a second such approach, three-dimensional objects are formed by successively cutting object cross-sections having desired shapes and sizes out of sheets of material, and then adhering the resulting cross-sections together to form the object. Typical of this approach is Laminated Object Manufacturing, as described in U.S. Pat. No. 4,752,352 to Feygin, in which the material is paper, and the means for cutting the sheets into the desired shapes and sizes is a CO.sub.2 laser.
Various issues arise with respect to the foregoing approaches however. Though the approach involving a photopolymer and UV laser has come into wide use and produces highly accurate objects, the use of photopolymers presents handling, disposal and toxicity issues. Furthermore, where lasers are used in any of the above approaches, safety concerns exist.
In addition, systems embodying any of the foregoing approaches may be generally expensive to purchase and operate because, for example, components such as lasers and scanning mirror systems are themselves expensive and/or need replacement or calibration over time. Furthermore, any of the foregoing approaches may require too much space and/or require a high level of expertise in operating the building apparatus which may prohibit their use in a typical office setting.
More recently, a third such approach to rapid prototyping and manufacturing has emerged. According to this approach, an object cross-section is formed by selectively depositing an unsolidified, flowable material onto a working surface in desired patterns in areas which will become part of the object cross-section, and then allowing or causing the material to form the object cross-section and simultaneously adhere to a previously-formed object cross-section. These steps are then repeated to successively build up the three-dimensional object cross-section by cross-section. This third approach may be called selective deposition modeling (SDM) due to the manner in which object formation occurs.
Typical of this approach is Thermal Stereolithography as described in U.S. Pat. No. 5,141,680 to Almquist et al. Also typical of this approach is Fused Deposition Modeling as described in U.S. Pat. Nos. 5,121,329 and 5,340,433 to Crump in which a thermosettable material is dispensed while in a molten state and then hardens after being allowed to cool. Another example is described in U.S. Pat. No. 5,260,009 to Penn. Another example is Ballistic Particle Manufacturing as described in U.S. Pat. Nos. 4,665,492; 5,134,569 and 5,216,616 to Masters, in which particles are directed to specific locations to form object cross-sections.
Thermal stereolithography is particularly suitable for use in an office environment because non-reactive, non-toxic materials can be used. Moreover, the process of forming objects using these materials need not involve the use of radiations (e.g. UV radiation, IR radiation and/or laser radiation), heating materials to combustible temperatures (e.g. burning the material along cross-section boundaries), reactive chemicals (e.g. photopolymers) or toxic chemicals (e.g. solvents & the like), complicated cutting machinery, and the like, which can be noisy or pose significant risks if mishandled. Instead, object formation is achieved by heating the material to a flowable temperature then selectively dispensing the material and allowing it to cool.
A critical problem that exists in relation to thermal stereolithography and the like involves finding suitable materials that are capable of being dispensed from the dispensers currently used in such systems (such as an ink jet print head), and which are also capable of forming three-dimensional objects with suitable strength and accuracy once they have been formed. In many situations, these materials must also be suitable for forming support structures for the object being formed.
An additional problem that exist in thermal stereolithography and the like is the need to quickly solidify the flowable material after its dispensed. The time necessary to remove heat sufficient for material solidification can limit the ability to lay a next layer, since newly dispensed material may deform or remelt insufficiently cooled previously deposited layers. This time required for removal of heat from the material can increase the overall object build time.
Hot melt inks developed for dispensing through ink jet print heads and the like are generally designed for printing text on paper. These materials are not designed for and are not suitable for thermal stereolithography because they lack strength, tend to be brittle, and exhibit significant layer to layer distortion.
Pattern waxes suitable for use in investment casting are also generally not suitable for thermal stereolithography. These materials tend to have high viscosities, relatively low toughness, or other properties which makes them difficult to handle and dispense from multi-orifice ink-jet dispensers such as those which may be used in thermal stereolithography. High material viscosity also reduces the ability to build accurate parts. The few pattern waxes in the appropriate viscosity range, such as the Kindt-Collins "PROTOWAX", exhibit relatively high layer to layer distortion. Further, these previous materials tend to have latent heat properties that are not suitable for quick heat dissipation and fast three-dimensional object building.
Other materials that may have properties suitable for either building of the three-dimensional object or for the support structures are not suitable as a single material for both the object and its supporting structures. These materials are either too brittle or too tough such that support removal is difficult and time consuming.
For all the foregoing reasons, there is an unmet need for a material suitable for use in Thermal Stereolithography which is capable of being jetted through an appropriate dispenser (such as multi-orifice, ink-jet type print head), and has the toughness, handling, and dimensional stability properties appropriate for three-dimensional modeling. The material should also have a broad temperature of solidification as well as not being subject to significant layerwise distortion due to shrinkage, curing, or other effects during the part building process. The material should also have a low latent heat of transformation.
3. Related Patents and Applications
The assignee of the subject application, 3D Systems, Inc., has filed the following related applications (now abandoned) all of which are incorporated by reference herein as though set forth in full:
______________________________________ Filing Date Application No. Title ______________________________________ 9/27/95 08/534,813 Selective Deposition Modeling Method and Apparatus for Forming Three- Dimensional Objects and Supports 9/27/95 08/534,447 Method and Apparatus for Data Manipulation and System Control in a Selective Deposition Modeling System 9/27/95 08/534,477 Selective Deposition Modeling System and Method ______________________________________
U.S. patent application Ser. No. 08/534,813 is directed to object and support build styles and structures for use in SDM.
U.S. patent application Ser. No. 08/534,447 is directed to data transformation techniques for use in converting 3D object data into support and object data for use In a preferred SDM system (e.g., thermal Stereolithography system). This application is also directed to various data handling, data control, and system control techniques for controlling the preferred system. Alternative data manipulation techniques and control techniques are also described for use in both SDM systems as well as for use in other RP&M systems.
U.S. patent application Ser. No. 08/534,477 is directed to the overall mechanical, electrical, thermal and material feed configuration and method of a preferred SDM system and in particular a preferred Thermal Stereolithography system. Some alternative configurations and methods are also addressed.
The assignee of the instant application, 3D Systems, Inc., is also the assignee of a number of other U.S. Patent Applications and U.S. Patents in RP&M and particularly in stereolithography. The following commonly owned U.S. Patent Applications and U.S. Patents are hereby incorporated by reference as if set forth in full herein.
______________________________________ App. No. Topic Status ______________________________________ 08/484,582 Basic Stereolithography 5,573,722 O8/475,715 Recoating Dispenser 5,667,820 08/473,834 Building Techniques 5,711,911 08/479,875 Building with Sheets Abandoned 08/486,098 Curl Reduction Techniques Abandoned 08/475,730 Boolean Layer Comparison Slice Pending 08/480,670 Slice Pending 08/428,950 Building Techniques/Quickcast Abandoned 08/428,951 Simultaneous Multiple Layer Curing Pending 08/405,812 Vibrational Recoating Techniques 5,688,464 08/402,553 Doctor Blade/Liquid Level Control Abandoned 08/382,268 Rapid Recoating Techniques Abandoned 07/182,801 Support Structures 4,999,143 07/183,015 Stress Reliefs 5,015,424 07/365,444 Integrated Stereolithography 5,143,663 07/749,125 Dispensing Material via Ink Jet 5,174,943 07/824,819 SLA-500 5,182,715 07/605,979 Extra Steps 5,209,878 07/929,463 Powder Coating 5,234,636 07/939,549 Curl Balancing 5,238,639 07/967,303 Method of Dispensing Materials via lnk Jet 5,344,298 ______________________________________